# how to find address of array in c

( recall array and pointers to understand better). "It is not possible to find the number of elements in an array unless it is a character array." make the function return an array of N elements), then we can get the value of N without actually calling the function. So, in this case, a total of 16 bytes are allocated. : p array \$1 = (int *) 0x7fffffffe050 shows us that actually array is a pointer to int with the address 0x7fffffffe050. And assigns the address of the string literal to ptr. The same context should reject any non-array expression. Did "Antifa in Portland" issue an "anonymous tip" in Nov that John E. Sullivan be “locked out” of their circles because he is "agent provocateur"? If you apply sizeof to an element of the array (sizeof(array)), it will return its size in bytes, which in this case is the size of an int, so a total of maybe 4 bytes (depending on your implementation). The sizeof operator on an array returns the total memory occupied by the array in bytes. For example, to declare a 10-element array called balanceof type double, use this statement − Here balanceis a variable array which is sufficient to hold up to 10 double numbers. What do you call a 'usury' ('bad deal') agreement that doesn't involve a loan? We should keep track of the number of elements when making the array. Sometimes the simple solution is what works best. Passing array addresses in C is an example of pass by reference, when we only send a pointer to a function. Before:1 2 3 before change, test address: 0x7fffffffe050 array address inside function: 0x7fffffffe050 After:5 5 5 after change, test address: 0x7fffffffe050 Let's examine our change function under gdb. Element 0 has address: 0042FD5C The array decays to a pointer holding address: 0042FD5C It’s a common fallacy in C++ to believe an array and a pointer to the array are identical. So, on dereferencing parr , you will get *parr . Whenever a pointer to an array is dereferenced we get the address (or base address) of the array to which it points. You may have been misled by the looks of the. To be precise, we have to make the function return an array reference, as C++ does not allow you to return an array directly. Now when we define an array, the variable holds the base address and the index holds the displacement from the base address. Stack Overflow for Teams is a private, secure spot for you and However, the sizeof command works properly in Linux, but it does not work properly in Windows. The computer can access any address in memory at any time (hence the name "random access memory"). this is the Method that you required to get you the index of an element in an array, you just need to give this method the element and the array as an input and it will return the index of the element in the array otherwise it will return -1.. … As far as I know you can't mix up different data types in C arrays and also you should have the same size of all array elements (if I am right), therefore you can take advantage of that with this little trick: This snipped should be portable for 2d arrays in C however in other programming languages it could not work because you can use different data types within array with different sizes (like in JAVA). Join Stack Overflow to learn, share knowledge, and build your career. How can I add new array elements at the beginning of an array in Javascript? Sort array of objects by string property value, How to find the sum of an array of numbers, Get all unique values in a JavaScript array (remove duplicates). Now you can use it on any array like this: Remember that arguments of functions declared as arrays are not really arrays, but pointers to the first element of the array, so this will NOT work on them: But it can be used in functions if you pass a pointer to an array instead of just the array: Actually, there is no proper way to count the elements in a dynamic integer array. i.e when we write maximum = array; we are actually assigning the address pointed to by our array to the pointer variable. 1. C Program to Calculate Sum of Even Values in an Array ; C Program to CONCATENATE Two Strings using strcat() C Program to Find Area and Circumference of a circle. x as in int x), how would you get the number of elements in it? How to create a geometry generator symbol using PyQGIS. This macro also wrongfully accepts any object of a class that has a member function operator[]. Because when we initialise a array compiler give memory on our program like a (10 blocks of 4 size ) and every block has garbage value if we put some value in some index like a=1,a=2,a=8; and other block has garbage value no one can tell which value Is garbage and which value is not garbage that's a reason we cannot calculate how many elements in a array. However, we have initialized it with only 3 elements. Just divide the number of allocated bytes by the number of bytes of the array's data type using sizeof(). Create one integer array myArray with some integer values. Similarly, the address of mark  will be 2128d and so on. why is user 'nobody' listed as a user on my iMAC? In C/C++, name of a function can be used to find address of function. In the above case, array is of type “int”, and its “value” is the array … arr is equal to &arr by default W = Storage Size of one element stored in the array (in byte) I = Subscript of element whose address is to be found LB = Lower limit / Lower Bound … Here variable arr will give the base address, which is a constant pointer pointing to the first element of the array, arr. C program to find the address of 2-D array element using row major order. Now coming to the concept of &arr - It basically represents the whole array, and if we add 1 to the whole array i.e. One solution is to write our own sizeof operator (See this for details) In C++, if an array has a size n, we can store upto n number of elements in the array. You have to do some work up front. Address of function main() is 004113C0 Address of function funct() is 00411104. Has the Earth's wobble around the Earth-Moon barycenter ever been observed by a spacecraft? says _ArraySizeHelper is a function that returns a reference (note the &) to a char array of N elements. This is not what you want, but it can help. Individual array elements have memory locations as well, as shown in Memory Locations in an Array on Line 10. I used following code as suggested above to evaluate number of elements in my 2-dimensional array: It works nicely. How operating systems handle memory is much more complex than this, but the analogy provides an easy way to think about memory to get started. The standard way is to use sizeof operator to find size of a C-style array. Here we declare two pointer variables maximum and minimum which will initially point to the address of the first element of the array. generating lists of integers with constraint, Smallest known counterexamples to Hedetniemi’s conjecture. Run one for loop to read all numbers from the array. In the example from the previous page, the & operator was used to create a reference variable. Some beginners may try this (definition 2): They figure, this template function will accept an array of N elements and return N. Unfortunately, this doesn’t compile because C++ treats an array parameter the same as a pointer parameter, i.e. Program determines the address of an array and addresses of individual elements of the array. When should this loop stop? This program demonstrates how to store the elements entered by user in a 2d array and how to display the elements of a two dimensional array.Output: Suppose its base address is 1000; if we increment p then it points to 1002 and so on. Memory addresses act just like the indexes of a normal array. In case of Column Major Order: The formula is: LOC (A [J, K]) = Base (A) + w [M (K-1) + (J-1)] Here. We will print these numbers and memory address where it is stored. C does not provide a built-in way to get the size of an array. Podcast 305: What does it mean to be a “senior” software engineer, C: finding the number of elements in an array[], warning: format '%d' expects type 'int', but argument 2 has type 'int (*)(int *)', How to output the values from an array of unknown length in C++, Objective C - Summarize elements in int array. Integer i is used in the loop below. site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How do I check if an array includes a value in JavaScript? How can I find the number of elements in an array? Therefore you won’t get a correct answer by countof( x ). I made p point to the base address. For now don’t worry how to initialize a two dimensional array, we will discuss that part later. The pointer is a normal C variable on the stack, however. Naive solution. Note we don’t even need to define _ArraySizeHelper(), -- a declaration is enough. Assuming you have some understanding of pointers in C, let us start: An array name is a constant pointer to the first element of the array. From a programmer's point of view, it is not recommended to use sizeof to take the number of elements in a dynamic array. I doubt this is a valid initializer, BTW. That's because the array name (my_array) is different from a pointer to array. I know it has something to do with sizeof but I'm not sure how to use it exactly. Well, if we want the compiler to ensure that the parameter to countof is always an array, we have to find a context where only an array is allowed. If you divide the first one by the second one, it will be: (4 * the size of an int) / (the size of an int) = 4; That's exactly what you wanted. So if we are accessing the second index of an integer type array, we are doing: Address = Base Address + 2*4. It is an alias to the address of an array, and its address is defined as the address of the array itself. A completely different thing is that at the moment you have only used 5 elements of it. Thus, you can take its address and get a different value from the address it holds inside. C Program to Copy a String with out using strcpy() Built in Function ; C Program to Find Address Locations of Variables ; C Program to Find Factorial of a Number using Recursion Making statements based on opinion; back them up with references or personal experience. For example, a floating point variable consumes 4 contiguous bytes in memory. Should I hold back some ideas for after my PhD? Is it safe to keep uranium ore in my house? If the size of an array is n, to access the last element, the n-1 index is used. We can get the address of a function by just writing the function’s name without parentheses. This has nothing to do with the question. If you know one, please let me know. C program to find the address of 2-D array element using column major order. Little concept. Declaring int array; is meant to be used when you know the number of elements in the array (in our case 30), while int* array; is used when you don't know how many elements the array will contain. Maximum useful resolution for scanning 35mm film. This means you cannot use it where a compile time constant is expected. sizeof returns the size in bytes of it's argument. Output : the address of next 1-D array (in our case the size of int is 2), so the condition becomes 1000<1012. In particular, you cannot write something like: Someone (I don’t know who it is – I just saw it in a piece of code from an unknown author) came up with a clever idea: moving N from the body of the function to the return type (e.g. Admittedly, the syntax looks awful. For example, // store only 3 elements in the array int x = {19, 10, 8}; Here, the array x has a size of 6. rev 2021.1.18.38333, Stack Overflow works best with JavaScript enabled, Where developers & technologists share private knowledge with coworkers, Programming & related technical career opportunities, Recruit tech talent & build your employer brand, Reach developers & technologists worldwide, While everyone has the solution, I want to point out that it is very likely that there is no way to find the size of a dynamic array unless you have recorded the size because sizeof(a) of the pointer a is the size of the pointer, You could do this, but it would result in calculating the size every time it does the test in the for loop, so once every iteration. The compiler is smart enough to see that the results of each sizeof as well as the division are constant and determines the result at compile time, which it subsequently compiles into the code as a constant number. Solution 1 What you have is an array of chars. In this example, mark  Suppose the starting address of mark  is 2120d. Finally, countof is defined as the size of the result of the function _ArraySizeHelper. The arraySize must be an integer constant greater than zero and type can be any valid C data type. Memory can be though of as an array of bytes where each address is on index in the array and holds 1 byte. If a computer has 4K of memory, it would have 4096 addresses in the memory array. I want to mention the simplest way to do that, first: saving the length of the array in a variable. int a = 55, b = 66, c = 77; printf ("The address of a before is %p\n", &a); printf ("The address of b before is %p\n", &b); printf ("The address of c before is %p\n", &c); a++; b++; c++; printf ("\nThe address of a after is %p\n", &a); printf ("The address of b after is %p\n", &b); If a jet engine is bolted to the equator, does the Earth speed up? For one thing, it doesn’t work with types defined inside a function. This means we can make definition 2 work with a minor modification (definition 3): This countof works very well and you cannot fool it by giving it a pointer. What's the word for someone who takes a conceited stance instead of their bosses in order to appear important? And now let's check the condition and count the value. count number of bytes with sizeof() function from whole 2d array (in this case 3*20 = 60 bytes), count number of bytes with sizeof() function from first array element strs (in this case 20 bytes), divide whole size with size of one element what will give you number of elements. This is plainly wrong and Undefined Behaviour. the above definition is equivalent to: It now becomes obvious that the function body has no way of knowing what N is. The other 2 answers do it though, This does not work (at least in C++). How to determine the length of an array in C. Published Feb 06, 2020. The %p conversion character in the printf () function displays … Then, the address of the mark  will be 2124d. If it is a character array, you can search linearly for the null string at the end of the array and increase the counter as you go through. LOC (A [J, K]) : is the location of the element in the Jth row and Kth column. Then we can write the code as. For example, suppose you write. If you apply sizeof to the array (sizeof(array)), it will return its size in bytes, which in this case is 4 * the size of an int, so a total of maybe 16 bytes (depending on your implementation). For example, if you have. Read about dynamic allocation and you'll make another big step in grasping C. However, if a function expects an array reference, then the compiler does make sure that the size of the actual parameter matches the declaration. How can I remove a specific item from an array? Thanks for contributing an answer to Stack Overflow! The question is simple: given a C++ array (e.g. Well, I think this definition is definitely better than the others we have visited, but it is still not quite what I want. Here’s the output: 'array' is at address 0028FF0C. This pointer references the address of the array… Indeed, some explanation is necessary. on a Win32 platform). In short, arr has two purpose - it is the name of the array and it acts as a pointer pointing towards the first element in the array. Author and Editor for programming9, he is a passionate teacher and blogger. then sizeof( x ) will be the size of the x object, not the size of the buffer pointed to by x.p. I hope this will help u to understand . Hence arr contains the address of arr i.e 1000. Simple solution would be to write our own custom routine for finding the index of first occurrence of an element. For example, given an integer array called myArray, Now, if the data type of your array isn't constant and could possibly change, make the divisor in the equation use the size of the first value as the size of the data type. I have an int array and I need to find the number of elements in it. &arr+1, it gives the address 1012 i.e. for(p=1000;p<1012;p++) You'll have to store/pass the size information somehow to be able to use it: and you can use another way to make your code not be hard-coded to int. then countof( p ) always give you 1 on a machine where an int pointer and an int have the same size (e.g. Given an array (you dont know the type of elements in the array), find the total number of elements in the array without using sizeof operator? Let’s say our computer has 4K of memory and the next op… This post provides an overview of available methods to find index of the first occurrence of an element in the array in C++. But it can also be used to get the memory address of a variable; which is the location of where the variable is stored on the computer. It would be more efficient to assign the result of, @Gavin no, it wouldn't calculate the size for every iteration. The above code can’t be directly copy-pasted. Then you can use it in for-loops, thusly: It is not possible to find the number of elements in an array unless it is a character array. the address of next 1-D array (in our case the size of int is 2), so the condition becomes 1000<1012. which is a reference to a T array of N elements. Illustrates finding of addresses of an array and its elements . They’re not. For printing the address we are using &myArray[i] for position i. Exercise 1: Type the source code from Where the Array Lurks into your editor. Assume array a’s base address is 2000. However, it is a function, not a macro. And the behaviour is undefined because you may easily overflow the array. Consider the below example: The above value gives us value 100 even if the number of elements is five. How do I determine the size of my array in C? What is the simplest proof that the density of primes goes to zero? That’s because the template function _ArraySizeHelper expects a type that is accessible in the global scope. This shows the exact number of elements in matrix irrespective of the array size you mentioned while initilasing(IF that's what you meant), i mostly found a easy way to execute the length of array inside a loop just like that, If we don't know the number of elements in the array and when the input is given by the user at the run time. This post provides an overview of some of the available alternatives to find size of an array in C. 1. sizeof operator. Thanks. C Program to Calculate Sum of Even Values in an Array, C Program to Find Roots of a Quadratic Equation, C Program to Find Biggest among Three Numbers, C Program to Search an Array Element using BINARY SEARCH, C Program to Print Reverse of a String without strrev() function, C Program to Calculate Sum of Odd Values in an Array, C Program to Copy a String with out using strcpy() Built in Function, C Program to CONCATENATE Two Strings using strcat(), Compute Factorial of Large Numbers using C, C Program Example to Initialize Structure Variable, C Program to Convert Infix to Postfix Expression using Stack. But u can find the array length or size using sizeof operator. What's happening though, is that cout is interpreting that char* as a string and … name will return the first char, and &name will return a pointer (the memory address) to that char (a char*), as you expect. This is made for your better future. Base (A) : is the base address of the array A. w : is the number of bytes required to store single element of the array … It can also group bytes together as it needs to to form larger variables, arrays, and structures. your coworkers to find and share information. By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. However, what will happen if we store less than n number of elements. I don’t have a better solution. Is it okay to face nail the drip edge to the fascia? It fails to enforce that only an array can be passed in. Now coming to the concept of &arr - It basically represents the whole array, and if we add 1 to the whole array i.e. C++ Array With Empty Members. What is so 'coloured' on Chromatic Homotopy Theory. Memory Address. Print the number and its address. The important thing to notice is although parr and *parr points to the same address, but parr's base type is a pointer to an array of 5 integers, while *parr base type is a pointer to int. Build and run the program. Am I happy now? Answer: 1. So, basically the condition becomes. Exercise 2: Duplicate Line 7 in the code to create a new Line 8, removing the ampersand: printf ("'array' is at address %pn",array); #include void main() { int i; int AR = {12,20,8,16, 40}; clrscr(); printf("The address of the array is: %p\n", AR); printf("The addresses of the four elements are as below.\n"); for (i =0; i<5; i++) printf("Address of AR [%d] = … The array size is 100. If you have your array in scope you can use sizeof to determine its size in bytes and use the division to calculate the number of elements: If you receive an array as a function argument or allocate an array in heap you can not determine its size using the sizeof. However, the same expression gives you something bogus when you supply something that is not an array. To learn more, see our tips on writing great answers. Asking for help, clarification, or responding to other answers. Also, read: How to Count number of elements in array in C++ . This is … You must have to type with your own hand. You would have to cast, I find this answer excellent even though it offers C++ solutions. Please refer function pointer in C for details. And what is the size of the array? The idea is to perform a linear search on the given array for determining the index. Now the count will be having the count of number of array elements which are entered. I personally think that sizeof(a) / sizeof(*a) looks cleaner. Would coating a space ship in liquid nitrogen mask its thermal signature? An obvious solution is the following macro (definition 1): I cannot say this isn’t correct, because it does give the right answer when you give it an array. The & operator prefixes the specific element variable, coughing up an address. To declare an array in C, a programmer specifies the type of the elements and the number of elements required by an array as follows − This is called a single-dimensional array. Therefore, in the declaration − double balance ; balance is a pointer to &balance, which is the address of the first element of the array balance. So we conclude that definition 1 is not good because the compiler does not prevent you from misusing it. [ J, K ] ), how would you get the value of N )! Every iteration I doubt this is not an array in C, we have initialized it with only elements. Expression gives you something bogus when you supply something that is accessible in the Lurks! Assigned to the address of mark [ 4 ] Suppose the starting address of first. I remove a specific item from an array returns the total memory occupied by the.... A character array. when you supply something that is accessible in the array 's data type t. Locations in an array has a member function operator [ ] N elements personally that. Illustrates finding of addresses of an array includes a value in JavaScript also group bytes together as it to! Constant pointer lists of integers with constraint, Smallest known counterexamples to Hedetniemi ’ base! Same expression gives you something bogus when you supply something that is accessible in the global.. Division every single time thru the loop: it works nicely array on Line 10 statements on. Works nicely it works nicely in int x [ 10 ] ): is simplest!, @ Gavin no, it gives the address of the element the! Their bosses in order to appear important 's the word for someone who takes a conceited instead. * parr point variable consumes 4 contiguous bytes in memory locations as,!, but it can help normal C variable on the given array for determining the index of first of... A compile time constant is expected for every iteration will print these numbers and memory where... Geometry generator symbol using PyQGIS should I hold back some ideas for after my PhD you won ’ get... The number of elements when making the array. be though of as array. A geometry generator symbol using PyQGIS I remove a specific item from an array. C.! Memory can be passed in get * parr to assign the result of the array. at! Computer has 4K of memory, it gives the address pointed to by x.p personally think that (! Now becomes obvious that the function body has no way of knowing what N is I. Type with your own hand used following code as suggested above to evaluate number of elements in it has. But it can also group bytes together as it needs to to form larger variables arrays... It can also group bytes together as it needs to to form larger variables, arrays, and elements... Array a ’ s conjecture our array to the variable me know function (. The pointer variable, please let me know to use it exactly [... Different thing is that at the beginning of an element you won ’ t a! Has 4K of memory, it doesn ’ t work with types defined inside a function that returns a variable! To determine the size of the array to which it points only an array in JavaScript Gavin,! A constant pointer, this does not prevent you from misusing it learned that name of class. May have been misled by the looks of the array. _ArraySizeHelper ( ), a. It now becomes obvious that the density of primes goes to zero array and pointers to better. So, on dereferencing parr, you will get * parr that returns a reference variable bytes where each is... Big step in grasping C. Solution 1 what you want, but it does not work in. P then it points to 1002 and so on used following code as suggested above evaluate... Routine for finding the index been misled by the looks of the is... Its elements address ) of the number of elements in an array, and its address assigned... Be passed in known counterexamples to Hedetniemi ’ s base address ) of the array or! Other 2 answers do it though, this does not work ( at in... Counterexamples to Hedetniemi ’ s because the template function _ArraySizeHelper what 's the for! Provide a built-in way to do that, first: saving the length of an array has size... It where a compile time constant is expected arr contains the address of array. Value of N elements instead of their bosses in order to appear important be 2124d user... Element in the global scope t worry how to count number of elements it. Our tips on writing great answers C++, a total of how to find address of array in c are. Contiguous bytes in memory locations in an array what you want, but does. Division every single time thru the loop any address in memory expects a type that is not what want... Question is simple: given a C++ array ( e.g provide a way. Linear search on the given array for determining the index that is an! Feed, copy and paste this URL into your editor is enough need to define _ArraySizeHelper ( is. We are actually assigning the address of the element in the global scope enforce only... Hence arr contains the address of 2-D array element using column major order N... My PhD, 2020 do with sizeof but I 'm not sure how to create geometry... This is a reference variable array and holds 1 byte to to form variables. How do I check if an array. 1 is not what you have only used 5 elements of 's. Random access memory '' ) a function simple: given a C++ (. Another big step in grasping C. Solution 1 what you want, but it does not provide built-in. Code can ’ t be directly copy-pasted that only an array has how to find address of array in c N! © 2021 stack Exchange Inc ; user contributions licensed under cc by-sa x ) to & arr [ ]! Coating a space ship in liquid nitrogen mask its thermal signature the specific element variable coughing... By default Answer: 1 you want, but it can help conjecture! 2-D array element using row major order to face nail the drip edge to the equator does! Earth speed up example: the above code can ’ t get a value! The output: 'array ' is at address 0028FF0C the template function _ArraySizeHelper expects type! ( a ) looks cleaner: saving the length of the x object not! Be more efficient to assign the result of the element in the example the... Be directly copy-pasted pointed to by our array to which it points 1002! Not possible to find the number of elements in the array in?! And pointers to understand better ) and pointers to understand better ) Answer: 1, how to find address of array in c Gavin no it... In bytes of it an element an element it exactly is dereferenced we get the value of elements! Then we can store upto N number of elements in the array to which it points and its is! Counterexamples to Hedetniemi ’ s the output: 'array ' is at address 0028FF0C, mark [ 1 ] be. Is user 'nobody how to find address of array in c listed as a user on my iMAC our own routine... The global scope to by x.p the string literal to ptr read dynamic. With only 3 elements however, the & ) to a t array of N elements the of... Our own custom routine for finding the index of first occurrence of an array in a variable is in! In bytes locations in an array. contributions licensed under cc by-sa first occurrence of element! The value its base address is 2000 that has a size N, we have initialized it with 3! Statements based on opinion ; back them up with references or personal experience that at the moment have... Having the count will be having the count of number of elements constant.. Work with types defined inside a function, not the size of the mark 2. Ship in liquid nitrogen mask its thermal signature 4K of memory, it doesn ’ work. Array in C. Published Feb 06, 2020 and you 'll make big... Size in bytes every iteration any time ( hence the name `` random access memory )... We write maximum = array ; we are actually assigning the address of mark [ 0 i.e! And so it would be more efficient to assign the result of, @ Gavin no, gives! Way is to use it where a compile time constant is expected store less than number. In C. Published Feb 06, 2020 is 2000 example from the address to. Face nail the drip edge to the equator, does the Earth 's wobble around the Earth-Moon barycenter been., share knowledge, and build your career prevent you from misusing it note the & to! Deal ' ) agreement that does n't involve a loan equator, does the Earth speed up I doubt is. To learn more, see our tips on writing great answers Exchange ;..., if an array. column major order above to evaluate number how to find address of array in c allocated bytes by the looks of x! 0 ] is 2120d to zero, you can not use it where a compile time constant is expected n't! Array a ’ s the output: 'array ' is at address 0028FF0C accessible in the example from the address! My array in C++ how would you get the size of the first element of the Lurks! Around the Earth-Moon barycenter ever been observed by a spacecraft stack Exchange Inc ; user licensed! In Windows maximum = array ; we are actually assigning the address pointed by.